Yes Temur, I tried. Same issue.

I edited my code while you was answering me, using the singleton instance of the ORM model (packaging_obj in my code) seems to be a better way to do it to me:

 @api.one
 def _set_product_tmpl_id_fnc(self):
     packaging_obj = self.pool.get('product.packaging')
     if len(self.product_tmpl_id.product_variant_ids) >= 1
     for product in self.product_tmpl_id.product_variant_ids
         packaging_copy = packaging_obj.copy_data(self.id)
         packaging_copy.write({'product_id':self.product_id})

But I got the following error message:

TypeError: copy_data() takes at least 4 arguments (2 given)

Here is the copy_data function signature

def copy_data(self, cr, uid, id, default=None, context=None): 

EDIT: Thanks Temur, I made several mistakes.

Here is the code I normally expected:

@api.one
def _set_product_tmpl_id_fnc(self):
    if len(self.product_tmpl_id.product_variant_ids) >= 1:
        for product in self.product_tmpl_id.product_variant_ids:
            packaging_copy_data = self.copy_data()
            print "packaging_copy_data :", packaging_copy_data
            packaging_copy_data.product_id = product.id
            packaging_copy_rec = self.create(packaging_copy_data)

But the error is raise immediately on the  "packaging_copy_data = self.copy_data()" line:

Traceback (most recent call last):
  File "/home/hugo/Projets/Projets_TecLib/odoo/openerp/http.py", line 530, in _handle_exception
    return super(JsonRequest, self)._handle_exception(exception)
  File "/home/hugo/Projets/Projets_TecLib/odoo/openerp/http.py", line 567, in dispatch
    result = self._call_function(**self.params)
  File "/home/hugo/Projets/Projets_TecLib/odoo/openerp/http.py", line 303, in _call_function
    return checked_call(self.db, *args, **kwargs)
  File "/home/hugo/Projets/Projets_TecLib/odoo/openerp/service/model.py", line 113, in wrapper
    return f(dbname, *args, **kwargs)
  File "/home/hugo/Projets/Projets_TecLib/odoo/openerp/http.py", line 300, in checked_call
    return self.endpoint(*a, **kw)
  File "/home/hugo/Projets/Projets_TecLib/odoo/openerp/http.py", line 796, in __call__
    return self.method(*args, **kw)
  File "/home/hugo/Projets/Projets_TecLib/odoo/openerp/http.py", line 396, in response_wrap
    response = f(*args, **kw)
  File "/home/hugo/Projets/Projets_TecLib/odoo/addons/web/controllers/main.py", line 937, in call_kw
    return self._call_kw(model, method, args, kwargs)
  File "/home/hugo/Projets/Projets_TecLib/odoo/addons/web/controllers/main.py", line 929, in _call_kw
    return getattr(request.registry.get(model), method)(request.cr, request.uid, *args, **kwargs)
  File "/home/hugo/Projets/Projets_TecLib/odoo/openerp/api.py", line 241, in wrapper
    return old_api(self, *args, **kwargs)
  File "/home/hugo/Projets/Projets_TecLib/odoo/addons/product/product.py", line 772, in write
    res = super(product_template, self).write(cr, uid, ids, vals, context=context)
  File "/home/hugo/Projets/Projets_TecLib/odoo/openerp/api.py", line 241, in wrapper
    return old_api(self, *args, **kwargs)
  File "/home/hugo/Projets/Projets_TecLib/odoo/addons/mail/mail_thread.py", line 431, in write
    result = super(mail_thread, self).write(cr, uid, ids, values, context=context)
  File "/home/hugo/Projets/Projets_TecLib/odoo/openerp/api.py", line 241, in wrapper
    return old_api(self, *args, **kwargs)
  File "/home/hugo/Projets/Projets_TecLib/odoo/openerp/api.py", line 363, in old_api
    result = method(recs, *args, **kwargs)
  File "/home/hugo/Projets/Projets_TecLib/odoo_addons_community/linked/connector/producer.py", line 61, in write
    result = write_original(self, vals)
  File "/home/hugo/Projets/Projets_TecLib/odoo/openerp/api.py", line 239, in wrapper
    return new_api(self, *args, **kwargs)
  File "/home/hugo/Projets/Projets_TecLib/odoo/openerp/models.py", line 3774, in write
    self._write(old_vals)
  File "/home/hugo/Projets/Projets_TecLib/odoo/openerp/api.py", line 239, in wrapper
    return new_api(self, *args, **kwargs)
  File "/home/hugo/Projets/Projets_TecLib/odoo/openerp/api.py", line 546, in new_api
    result = method(self._model, cr, uid, self.ids, *args, **kwargs)
  File "/home/hugo/Projets/Projets_TecLib/odoo/openerp/models.py", line 3917, in _write
    result += self._columns[field].set(cr, self, id, field, vals[field], user, context=rel_context) or []
  File "/home/hugo/Projets/Projets_TecLib/odoo/openerp/osv/fields.py", line 800, in set
    id_new = obj.create(cr, user, act[2], context=context)
  File "/home/hugo/Projets/Projets_TecLib/odoo/openerp/api.py", line 241, in wrapper
    return old_api(self, *args, **kwargs)
  File "/home/hugo/Projets/Projets_TecLib/odoo/openerp/api.py", line 336, in old_api
    result = method(recs, *args, **kwargs)
  File "/home/hugo/Projets/Projets_TecLib/odoo_addons_community/linked/connector/producer.py", line 47, in create
    record_id = create_original(self, vals)
  File "/home/hugo/Projets/Projets_TecLib/odoo/openerp/api.py", line 239, in wrapper
    return new_api(self, *args, **kwargs)
  File "/home/hugo/Projets/Projets_TecLib/odoo/openerp/models.py", line 4079, in create
    self._fields[key].determine_inverse(record)
  File "/home/hugo/Projets/Projets_TecLib/odoo/openerp/fields.py", line 935, in determine_inverse
    self.inverse(records)
  File "/home/hugo/Projets/Projets_TecLib/odoo/openerp/api.py", line 239, in wrapper
    return new_api(self, *args, **kwargs)
  File "/home/hugo/Projets/Projets_TecLib/odoo/openerp/api.py", line 397, in new_api
    result = [method(rec, *args, **kwargs) for rec in self]
  File "/home/hugo/Projets/Projets_TecLib/odoo_addons/auguria_scan_packaging/models/picking.py", line 42, in _set_product_tmpl_id_fnc
    packaging_copy_data = self.copy_data()
  File "/home/hugo/Projets/Projets_TecLib/odoo/openerp/api.py", line 239, in wrapper
    return new_api(self, *args, **kwargs)
  File "/home/hugo/Projets/Projets_TecLib/odoo/openerp/api.py", line 503, in new_api
    result = [method(self._model, cr, uid, id, *args, **kwargs) for id in self.ids]
  File "/home/hugo/Projets/Projets_TecLib/odoo/openerp/models.py", line 4697, in copy_data
    seen_map = context.setdefault('__copy_data_seen', {})
  File "/home/hugo/Projets/Projets_TecLib/odoo/openerp/tools/misc.py", line 1280, in setdefault
    raise NotImplementedError("'setdefault' not supported on frozendict")
NotImplementedError: 'setdefault' not supported on frozendic

Try:

 @api.one
 def _set_product_tmpl_id_fnc(self):
     if len(self.product_tmpl_id.product_variant_ids) >= 1
     for product in self.product_tmpl_id.product_variant_ids
         packaging_copy = self.copy_data() # no arguments here, id should be passed automatically.
         print "packaging_copy: ",packaging_copy ### See what it looks like, then adapt next line to it. I've doubts about next line...
         ### packaging_copy.write({'product_id':self.product_id})

...because, if packaging_copy is a record copy of self, then normally product_id should be same in packaging_copy as in the self... then what it changes to copy that field from original record to the copied record? at least check if such action is absolutely necessary. it may be a case that "product_id" considered as special field and is not copied with copy_data? then it's ok, otherwise no need for this line.

but if packaging_copy is a dictionary containing field values of self rather then the orm record, there will no write() method. in such a case you'll have to create duplicate record first, as follows:

         packaging_copy_record = self.create(packaging_copy)

so solution depends on the type of packaging_copy returned from copy_data... if it's a record, then you do not need the last line in your code fragment(of course if product_id is already copied and not skipped for some reason), but if it's a dictionary of field values then you'll need to add above create() statement...

UPDATE for code with singletone in your answer:

@api.one
 def _set_product_tmpl_id_fnc(self):
     packaging_obj = self.pool.get('product.packaging')
     if len(self.product_tmpl_id.product_variant_ids) >= 1
     for product in self.product_tmpl_id.product_variant_ids
         packaging_copy = packaging_obj.copy_data(self._cr,self._uid,self.id)
         ### packaging_copy.write({'product_id':self.product_id})

 
@api.one
 def _set_product_tmpl_id_fnc(self):
     packaging_obj = self.pool.get('product.packaging')
     # packaging_obj = self.env['product.packaging'] ### also an option...
     if len(self.product_tmpl_id.product_variant_ids) >= 1
     for product in self.product_tmpl_id.product_variant_ids
         packaging_copy = packaging_obj.copy_data(self._cr,self._uid,self.id, default={'product_id': product.id})
         print "packaging_copy: ",packaging_copy
         ### ...